


TwistedTale

by CreativePoptart



Category: Undertale (Video Game)
Genre: Blood and Gore, Body Horror, Not for the faint of heart, Serious Injuries, mutations
Language: English
Status: Completed
Published: 2019-04-25
Updated: 2019-04-25
Packaged: 2020-01-31 19:10:20
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,411
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18597613
Author URL: https://archiveofourown.org/users/CreativePoptart/pseuds/CreativePoptart
Summary: Something is amiss in the Underground, something terrible and painful. Sans tries to take a look at what the problem is so he can fix it, but there is too much for him to try and handle.





	TwistedTale

**Author's Note:**

> WARNING: The following story, while it does not contain violence of any kind does contain graphic detailing of body horror and disturbing imagery. Reader discretion is heavily advised.

No one had really known when it had happened, but some of the monsters said it happened all at once. Sans knew better than that, he knew it had happened gradually because something as horrific as this couldn’t just pop up overnight. Monsters all over the Underground were suffering, struggling just to get by through another day.

 

It had started with the Queen. 

 

Queen Toriel had always been a beacon of light for most of the monsters, but shortly following her self-imposed exile, there was the fading of said hope. Monsters didn’t exactly know where to turn for advice anymore, as the King was a broken shell and there was nothing anyone could really do to console him. The Queen’s absence was greatly felt among monsterkind, and there was so little hope left just from that.

 

Then it was the Royal Scientist, Alphys.

 

Sans had known Alphys for a good while when she stepped up to the plate, filling in the empty position of the Royal Scientist. He had even worked with her for a time, before personal reasons got in between them and he stepped down. She had created something for entertainment, to stave off boredom at the very least, Mettaton. He was something different, something unusual, and a welcome distraction from the mind numbing monotony that had become the Underground.

 

After she took up her position, however, Alphys began toying with something that probably should have been left alone for good. Playing with forces out of one’s control was never a good idea, but things spiralled out of control with every measure she took. It was simple enough in concept, made from human souls, and was something that, until brought to light from the previous scientist’s work, was vastly unknown to monsters.

 

Determination.

 

This was apparently the driving force behind human souls, the reason why they were so powerful and strong. Determination allowed their souls to persist after death, even if only for a few moments more, and kept humans going when all else seemed lost. A fascinating subject, and one that Sans had considered briefly studying as a few reports were made public.

 

As the discoveries came pouring in, however, the dominos started falling, knocking the next over one by one. 

 

It started with good enough intentions, Sans would give Alphys that much. Monsters who had fallen down would be given a small dosage of determination to try and boost their magic back into working order. For a time it seemed to work, leading to a great recovery with many who had initially given up on their lives. Alphys was ecstatic, contacting Sans about the good news each time there was a success. Despite him no longer being a presence at the lab, they were still pretty decent friends, or so he liked to think. 

 

And then… the worst thing to ever occur happened.

 

Sans noticed some odd behavior happening in the monsters in Snowdin, though he brushed it aside casually. There was a little more hope after the determination experiments had been made somewhat known to the public. That wasn’t what he was seeing. Monsters were… more twitchy than he remembered them being. Had the nice lady at the shop always looked like she had been scratching at her neck?

 

Alphys had also stopped responding to his texts, not picking up when he called her, and wouldn’t open the door to the lab when he shortcutted over there. The silence from her was a bit unsettling, but she had been known to cut herself off from the rest of the Underground when she was particularly enthused about something. Sans easily dismissed that as nothing too far out of the ordinary as well, though he began to grow worried after a week of radio silence from the scientist.

 

Undyne was the first to really become a concern to him, though he didn’t really see it as a problem in the beginning. She was coming over almost all the time anyway to check on him and Papyrus at their stations and to have cooking lessons. Now when she arrived though, Sans noted that she seemed uncomfortable, physically speaking. 

 

There was something about her that was just… off. Sure she was still loud, brash, and semi-destructive, but now something was definitely up. She didn’t normally shed scales, and certainly not in this quantity, so why was there a small collection that he found after a cooking lesson with Papyrus? He tried not to think too hard about it.

 

But he definitely should have.

 

Things started to happen more frequently, though it was in the little details that he really began to notice things happening. When did Gryftrot have fangs poking out of his mouth? Probably a growth spurt or something like that. Did Monster Kid always have such sharp spines on his back? Maybe it was just that he was getting ready to shed his stripes. Was Grillby always this warm when he came over to serve Sans? Perhaps he was feeling a bit under the weather today.

 

...Had Sans’ teeth always felt this sensitive in his mouth before?

 

The questions began to pile on up more and more until Sans was forced to actually take a look around at his surroundings and really look at them instead of brushing them aside. He started off in the middle of Snowdin, easy enough, but then as more things came to his attention, there were other places that he visited, searching for the key to what was happening. Answers that he found weren’t pretty, by any means.

 

The bunny monster at the inn looked sickly when Sans paid her a visit, with fur falling out in patches and her eyes bloodshot. Her usually trimmed nails were long and sharp, with her claiming in a pained voice that they just kept growing back like that. Her teeth,  _ stars _ her teeth, were long, cracked, and gnarled in her mouth, obstructing her speech and making her wince every time she started to say something.

 

Monster Kid was crying almost constantly from what little Sans actually saw of him. Poor kid didn’t even have arms, but now the spines that lined his back were sharper than before, twisting and curling back over his body and impaling him in some places, leaving bloodied trails. The skeleton had tried to offer his assistance, but MK simply told him to stay away. Sans also noticed that MK’s feet now looked like they faced two separate directions, which didn’t help the child’s problem of tripping over himself any.

 

More and more monsters were disfigured, unrecognizable in states of melting or strange mutations that couldn’t be explained. Doggo’s already blind eyes now were bleeding constantly, his nose and muzzle cracked with teeth growing in the wrong directions. All the dogs were suffering in similar manners, with Dogamy and Dogaressa sporting spikes of…  _ something _ that bled constantly on their heels. Lesser and Greater Dogs too were bleeding, and they scratched, shedding tangled, matted, bloody fur into the pristine snow on the ground.

 

Grillby was one of the harder ones to accept, being Sans’ closest friend and his compatriot through many things. Now, however, his flames were out of control, flaring wildly and changing colors so rapidly that it was hard to look at him sometimes. Tendrils of fire would often leap off of his person and lash out at anything nearby, until Grillby himself barred his establishment up, claiming he was no longer safe to be near others. Even from standing outside, he could hear the crackling of what sounded like a roaring fire, lapping at the building’s walls.

 

Undyne came around a few days later, and Sans hoped to the stars that she would never come by again, if only to spare Papyrus of the sight. She was melting, dripping everywhere and leaving a trail of blue and gray, her liquifying armor mixing in with the sludge of her body. Her voice was garbled into moaning and strained groans, but no longer capable of coherent speech as her mouth was now dripping into itself, strung shut with goopy flesh. Worst of all, she seemed to be one of the lucky ones.

 

Papyrus…  _ Stars _ , Papyrus was the last monster Sans would have expected to crack under the pressure of all the sudden changes the Underground was facing. His brother, unfortunately, was not immune to whatever was causing all of this to happen. The painful changes inflicted upon the bubbly, upbeat skeleton were some of the hardest for Sans to face.

 

It started with Papyrus’ hands. The phalanges at the ends of his hands down to the carpals of his wrists had always been of a thick nature, but now they seemed swollen, painfully so. Despite Sans pushing for his brother to rest, Papyrus refused to do so, working as hard as he could to try and fix whatever he could get his hands onto. Chips and cracks now lined the once strong bones on the taller skeleton’s hands, but that wasn’t the end of the problems.

 

Papyrus’ ribcage was the next issue that arose, when he told Sans that he felt like he was having trouble breathing, despite not needing to at all. Reluctantly, he stripped his armor to show Sans the worsening problem that he had hidden from view, and Sans was  _ mortified _ . His brother’s ribcage was slowly turning itself inside out, the false ribs curving backwards from where they should have been and the upper ribs twisted like streamers. Papyrus’ sternum was splitting in two in a jagged line, poking upwards and and pressing against the battle body that Sans had helped him make. It wasn’t too much longer after that that the poor costume ended up being shredded by the protruding and rough bones.

 

The nail in the coffin on Papyrus’ condition was his neck, and this was where Sans stopped looking for what was wrong, because it was getting to be too much. At first it seemed like Papyrus was just leaning his head to the side, being naturally inquisitive. A closer look, however, revealed to Sans that the fourth cervical vertebra in his brother’s neck was now growing at an angle, creating the perpetual tilt.

 

The younger skeleton had tried to fix it himself, going so far as to snap his neck back into place and tie his scarf tightly to it with a stick to support it. After only three days, however, Papyrus came to Sans, bawling in pain because of his neck, and Sans forced him to take it off. Now Papyrus couldn’t look at anything correctly due to the angle in his vision. The smaller skeleton also knew that his brother’s mouth was twisting, changing as well, but he could hardly bear to look at the way that the teeth were shifting out of place.

 

Sans hadn’t bothered to take a look at himself ever since he noticed Papyrus going through painful changes. The mirrors were hidden away, as his brother was sensitive about how he looked and didn’t much care for reminders. When Sans found that a tooth had fallen out of his mouth from doing nothing at all, he pulled one of them out to take a look at what exactly had been going on. 

 

In the place of where his tooth had been lay at least three razor sharp teeth in its place. They were fairly short and reminded him of needles, which made him drop the smaller mirror in abject horror. He quickly located another one to find that not only were his teeth different, but so were bones he couldn’t see. With a looming sense of dread and a growing panic, he looked over the damage that his body was undertaking in the mirror’s surface.

 

His clavicles now sported a strange set of bubbles underneath, giving the impression of a soda that had been shaken up. The blades of his shoulders were sharper, catching and tearing at his clothing whenever he shifted too much in one direction or the other. His feet were warped and the bones were bending out of place, making it painful for him to walk anywhere and forcing him to use his shortcuts more often. 

 

That was the final straw for Sans, as more and more of his teeth fell out, only to be replaced with several needle-like ones. It was more and more difficult to speak every single time one of the short, blunted teeth was replaced with their pointier counterparts. He shortcutted straight into Alphys’ lab, demanding to know an answer, but she wasn’t anywhere to be seen. With some effort, he made his way into her actual lab, only to discover that she had been affected as well. 

 

The monsters that had fallen down were all melded into strange amorphous shapes that oozed and bubbled, just like Undyne. Those monsters were now semi-fused into her scales, pulsing and changing shape before his eyes. She appeared to be the most intact out of everyone, but much of her body was covered in the white ooze. When she tried to explain it to Sans, her voice was melded into many others, creating a haunting echo.

 

As it turned out, the determination experiments had failed miserably, creating these white oozing amalgamations that now clung to her skin. In her attempts to help them, after they had changed and melted, the last vials of concentrated determination had been broken, which led them all to latch on to her. Over time, the determination had been leaking out of the lab, poisoning the monsters and the air around them, warping their bodies while their minds remained whole.

 

Mettaton, as she explained, had gone to visit Napstablook, and hadn’t returned since, and she feared that he was killed in the aftermath. Sans personally hadn’t seen them, but he knew that they were most likely still alive, if not horribly disfigured. Alphys also said that she hadn’t heard a single word from the King ever since this all began, and she broke down into a sobbing mess at his feet.

 

Sans couldn’t handle it anymore and took a shortcut back to Snowdin, rage clouding his vision. There was something that wanted to do more, but what could he do with raw, undiluted determination contaminating every inch of the Underground? He resigned himself to a quiet despair, clinging to the final thread of hope that someone, or something, could save them all from this.

 

They truly were monsters now, weren’t they?

**Author's Note:**

> This story was inspired by a starting AU from Under-Imagines on Tumblr! The ideas contained within this story are largely not my own, but there is a little artistic license in my writing about character descriptions and how things went down. This may get expanded into a Reader insert if I can think of something, but for now, this is just an idea that spawned from another idea!
> 
> Here is the URL for Under-Imagines: https://under-imagines.tumblr.com/post/184422701634/an-au-that-stemmed-from-my-intense-desire-to-have


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